A device for collecting and jointly folding a plurality of sheets of paper of unequal length by means of a collection station has been known (DE Utility Model No. G 94 04 431.7), in which the sheets of paper collected in the collecting station pass together through a buckle folding mechanism, which has at least one folding pocket with a paper stop equipped for performing lifting movements and is provided with at least one paper deflector arranged in front of another folding pocket.
The collecting station is provided with an electromagnetically controllable sheet-stopping means, which is arranged in a sheet conveyor track directed toward the draw-in point of the buckle folding mechanism. Between a plurality of conveying strands of endlessly running conveyor belts located above and under the sheet conveying track, the sheet conveyor track has a stacking ramp, by which the arriving sheets are placed one on top of another in front of the sheet-stopping means. Only one folding pocket is open and active in the buckle folding mechanism; the paper stop of this folding pocket is set to an intake depth corresponding to half the size length of the long sheet of paper, and is mounted elastically movably between two fixed end positions in the draw-in direction.
Long and short sheets of paper can be transported together through a buckle folding mechanism with this prior-art device, and they can be folded in the process such that one or more short sheets of paper are folded together into the long sheet of paper without being folded itself or themselves, in order to be subsequently stuffed into an envelope in an envelope-stuffing device, or to be sealed. The long sheets of paper may be introduced into the collecting station optionally before or after the short sheets of paper. The folding of these sheets of paper around the short sheet of paper running together with it may be optionally performed in the first or second folding pocket or folding point. This requires only a different programming of the electronic control device, which is commonly used in such plants anyway.
This device is unsuitable for collecting and folding in packets of a plurality of sheets of paper of equal length because the folding pocket located behind the draw-in point must be set to an intake depth that corresponds to the size length of the short sheets of paper, and a folding takes place each time a long sheet of paper is drawn in. The collection of the sheets of paper is also not performed with this device in a folding pocket, but in a collecting station, which is arranged upstream of the folding mechanism or its draw-in point, and which must have a sheet-stopping device of its own and requires a corresponding space.
A buckle folding machine with a plurality of pairs of folding rollers forming a folding point each has also been known (DE-A-41 14 105), which has a plurality of folding pockets associated with the individual folding points, and which folding pockets are provided with a paper stop each, which can be adjusted with its stop surface to stop planes which determine different lead lengths for the arriving material to be folded. To make it possible to use this buckle folding machine both as a conventional folding machine for folding individual sheets of paper running through and for collecting and jointly folding a plurality of sheets of paper, a folding pocket designed for simultaneously receiving a plurality of sheets of paper is arranged and designed such that the individual sheets of paper can run automatically up to the paper stop over their entire length and remain there. In addition, this folding pocket has a pushing means, which performs pulsed lifting movements by means of a special drive controlled by a presettable sheet-counting means or code-reading means, and the sheets of paper collected in that folding pocket are conveyed together into the next folding point by the pulsed lifting movements.
Since the collection of a plurality of sheets of paper takes place here in a folding pocket that is sloped downward in the intake direction for this purpose and is equipped with an ejector, satisfactory operation requires that all the collected sheets of paper have at least approximately the same length and that the intake depth be set to that length, so that a slight push is sufficient to push the sheets of paper collected in that folding pocket with their front edges facing the next folding point into that folding point, so that they will be grasped and further conveyed there. However, folding of the paper does not take place in this folding point. The folding can then be performed only by means of a subsequent folding pocket and subsequent additional folding points.
This device is unsuitable for jointly folding sheets of paper of unequal length. In addition, the first folding pocket, i.e., the folding pocket arranged directly behind the draw-in point, cannot be used as a collecting folding pocket in prior-art buckle folding machines, because this folding pocket rises in the intake direction, and the arriving sheets of paper would fall out immediately.
In another prior-art buckle folding machine (DE 3 830 754), the conveyor belts of a conveying means, which is arranged in front of the draw-in point formed by two draw-in rollers and is provided with a stacking ramp, are driven at a higher conveying speed than the two draw-in rollers in order to obtain the highest possible degree of overlap of the sheets of paper reaching the stacking ramp one after another. The sheets of paper arriving in the folding pocket, which is arranged directly behind the draw-in point with a residual offset, are thus not folded simultaneously, but staggered in time and offset in space in relation to one another in a folding point through which they pass vertically downwardly directed in order to be subsequently pushed automatically into one another in an approximately vertical position.
Aside from the fact that multiple folds cannot be made according to this method, the phenomenon of electrostatic charging, which highly compromises function, proved to be very disturbing in practice. The conveying and consequently the degree of overlap of the individual sheets of paper become uncontrollable due to the electrostatic charge of the individual sheets of paper, which is caused essentially by the sheets of paper sliding one on top of another with a friction. The sheets of paper stick together in the case of different overlaps, so that not all of them reach the stop in the folding pocket, and a completely uncontrollable folding is obtained. Consequently, this device is not reliable in operation.